revwalk: remove preallocation of the uninteresting commits

Preallocating two commits doesn't make much sense as leaving allocation
to the first array usage will allocate a sensible size with room for
growth.

This preallocation has also been hiding issues with strict aliasing in
the tests, as we have fairly simple histories and never trigger the
growth.

src/revwalk.c

@@ -48,9 +48,6 @@ static int mark_uninteresting(git_revwalk *walk, git_commit_list_node *commit)
 
 	assert(commit);
 
-	git_array_init_to_size(pending, 2);
-	GITERR_CHECK_ARRAY(pending);
-
 	do {
 		commit->uninteresting = 1;